U.S. patent application number 10/371262 was filed with the patent office on 2004-08-26 for photoresist composition for deep ultraviolet lithography.
Invention is credited to Dammel, Ralph R., Houlihan, Frank, Sakamuri, Raj.
Application Number | 20040166434 10/371262 |
Document ID | / |
Family ID | 32868306 |
Filed Date | 2004-08-26 |
United States Patent
Application |
20040166434 |
Kind Code |
A1 |
Dammel, Ralph R. ; et
al. |
August 26, 2004 |
Photoresist composition for deep ultraviolet lithography
Abstract
The present invention relates to a photoresist composition
comprising a photoacid generator and at least one novel polymer
comprising at least one unit as described by structure 1, 1 where,
either (i) R1 is an aliphatic cyclic unit of a polymer, R2 is
selected from H, F, (C1-C8)alkyl, (C1-C8)fluoroalkyl, cycloalkyl,
cyclofluoroalkyl, and (CR3R4)p(CO)OR5, and R.sub.f is selected from
F, H, (C1-C8)alkyl, or a fully or partially fluorinated alkyl, and
cyclofluoroalkyl, or (ii) R1 and R2 combine to form an aliphatic
cyclic unit of a polymer, and R.sub.f is selected from F, H,
(C1-C8)alkyl and a fully or partially fluorinated alkyl, and
cyclofluoroalkyl, or (ii) R1 and R.sub.f combine to form an
aliphatic cyclic unit of a polymer, and R2 is selected from H, F,
(C1-C8)alkyl, (C1-C8)fluoroalkyl, cycloalkyl, cyclofluoroalkyl, and
(CR3R4)p(CO)OR5; and, R3 and R4 are independently H, F,
(C1-C8)alkyl, (C1-C8)fluoroalkyl, cycloalkyl, cyclofluoroalkyl,
(CR3R4)p(CO)OR5, R3 and R4 may combine to form an alkylspirocyclic
or a fluoroalkylspirocyclic group, X is selected from
(C1-C8)alkylene, (C1-C8)fluoroalkylene, O(C1-C8)alkylene,
O(C1-C8)fluoroalkylene, cycloalkyl and fluorinatedcycloalkyl, R5 is
H or an acid labile group, m=0-1, and p=1-4. The invention also
relates to a process for imaging the photoresist composition of the
present invention.
Inventors: |
Dammel, Ralph R.;
(Flemington, NJ) ; Sakamuri, Raj; (Sharon, MA)
; Houlihan, Frank; (Millington, NJ) |
Correspondence
Address: |
Sangya Jain
Clariant Corporation
70 Meister Avenue
Somerville
NJ
08876
US
|
Family ID: |
32868306 |
Appl. No.: |
10/371262 |
Filed: |
February 21, 2003 |
Current U.S.
Class: |
430/270.1 ;
430/326; 430/907 |
Current CPC
Class: |
G03F 7/0046 20130101;
Y10S 430/111 20130101; G03F 7/0395 20130101; Y10S 430/108 20130101;
Y10S 430/106 20130101 |
Class at
Publication: |
430/270.1 ;
430/907; 430/326 |
International
Class: |
G03F 007/004 |
Claims
1. A photoresist composition comprising a photoacid generator and
at least one novel polymer comprising at least one unit as
described by structure 1, 6where, either (i) R1 is an aliphatic
cyclic unit of a polymer, R2 is selected from H, F, (C1-C8)alkyl,
(C1-C8)fluoroalkyl, cycloalkyl, cyclofluoroalkyl, and
(CR3R4)p(CO)OR5, and R.sub.f is selected from F, H, (C1-C8)alkyl,
or a fully or partially fluorinated alkyl, and cyclofluoroalkyl, or
(ii) R1 and R2 combine to form an aliphatic cyclic unit of a
polymer, and rf is selected from F, H, (C1-C8)alkyl and a fully or
partially fluorinated alkyl, and cyclofluoroalkyl, or (ii) R1 and
R.sub.f combine to form an aliphatic cyclic unit of a polymer, and
R2 is selected from H, F, (C1-C8)alkyl, (C1-C8)fluoroalkyl,
cycloalkyl, cyclofluoroalkyl, and (CR3R4)p(CO)OR5; and, R3 and R4
are independently H, F, (C1-C8)alkyl, (C1-C8)fluoroalkyl,
cycloalkyl, cyclofluoroalkyl, (CR3R4)p(CO)OR5, R3 and R4 may
combine to form an alkylspirocyclic or a fluoroalkylspirocyclic
group, x is selected from (C1-C8)alkylene, (C1-c8)fluoroalkylene,
O(C1-C8)alkylene, O(C1-C8)fluoroalkylene, cycloalkyl and
fluorinatedcycloalkyl, R5 is H or an acid labile group, m=0-1, and
p=1-4.
2. The composition according to claim 1, where the polymer
comprises an aliphatic cyclic fluoroalcohol unit functionalized
with an alkyloxycarbonylalkyl group.
3. The composition according to claim 1, where the cyclic unit is
an aliphatic multicyclic unit or an aliphatic monocyclic unit.
4. The composition according to claim 3, where the multicyclic unit
is selected from those derived from the following monomers, 7where,
in the above structures, R1-R7 are independently H, F,
(C1-C8)alkyl, (C.sub.1-C8)fluoroalkyl, etc but at least one of
R1-R6 has the pendant oxyAOCA functionality described in structure
1, or an alcohol functionality which can be capped to give the unit
of structure 1.
5. The composition according to claim 3, where the multicyclic unit
is selected from those derived from the following monomers, 89
6. The composition according to claim 3, where the monocyclic unit
is derived from functionalizing fluoroalcohols with an AOCA group,
and where the fluoroalcohols are selected from
7. The composition according to claim 6, where the fluoroalcohols
are selected from, 10Rf=fluoroalkyl group C.sub.1-C.sub.8 Y=alkyl
or fluoroalkyl spacer group C.sub.1-C.sub.8 Ra, Rb, Rc, Rd, Re,
Rg=alkyl, X.dbd.CF.sub.2, O fluoroalkyl or fluorocycloalkyl, Also,
Ra-Re and Rg can be substituted with alkyl, fluoroalkyl, cycloakyl,
fluorocycloalkyl or with a spirofluoroalkyl or spiroalkyl
subsituent
8. The composition of claim 2, where the alkyloxycarbonylalkyl
group is selected from t-butyloxycarbonylmethyl,
methyl-adamantyloxycarbonylmethyl- , t-amyloxycarbonylmethyl,
methyl-Inorbornyloxycarbonylmethyl, t-butyloxycarbonyl propyl and
t-butyloxycarbonyldifluorobutyl.
9. The composition of claim 1, where the acid labile group is
selected from secondary and tertiary alkyls (up to 20 carbon
atoms), acetals and ketals, trimethylsilyl, .beta.-trimethylsilyl
substituted alkyls, tetrahydrofuranyl, tetrahydropyranyl,
substituted or unsubstituted methoxymethoxycarbonyl, and
.beta.-trialkylsilylalkyl.
10. The composition of claim 1, where the polymer is selected from
poly(bicyclo[2.2.1]hept-5-en-2-yl)-1,1,1-trifluoro-2-(trifluoromethyl)pro-
pan-2-ol),
poly(1,1,2,3,3-pentafluoro-4-trifluoromethyl-4-hydroxy-1,6-hept-
adiene and
poly(1,1,2,3,3-pentafluoro-4-trifluoroalkyl-4-hydroxy-1,6-hepta-
diene).
11. The composition of claim 1, where the polymer comprises a
mixture of polymers comprising monocyclic units and polymers
comprising multicyclic units.
12. The composition of claim 11, where the mixture is
poly(bicyclo[2.2.1]hept-5-en-2-yl)-1,1,1-trifluoro-2-(trifluoromethyl)pro-
pan-2-ol) with poly(1,1,2,3,3-pentafluoro
4-trifluoromethyl-4-hydroxy-1,6-- heptadiene).
13. The composition of claim 1, where the composition further
comprises a dissolution inhibitor.
14. The composition of claim 1, where the composition further
comprises a base.
15. The composition of claim 1, where the photoacid generator is
selected from diazonium salts, iodonium salts, sulfonium salts,
triazines, oxazoles, oxadiazoles, thiazoles, substituted 2-pyrones
and phenolic sulfonic esters.
16. A process for imaging a photoresist composition comprising the
steps of: a) forming on a substrate a photoresist coating from the
photoresist composition of claim 1; b) image-wise exposing the
photoresist coating; c) postexposure baking the photoresist
coating; and d) developing the photoresist coating with an aqueous
alkaline solution.
17. The process of claim 16, where the image-wise exposure
wavelength is below 200 nm.
18. The process according to claim 16, where the aqueous alkaline
solution comprises tetramethylammonium hydroxide.
19. The process according to claim 16, where the aqueous alkaline
solution further comprises a surfactant.
Description
FIELD OF INVENTION
[0001] The present invention relates to a novel photoresist
composition that is particularly useful in the field of
microlithography, and especially useful for imaging positive
patterns in the production of semiconductor devices. The
photoresist resin composition comprises a polymer or a mixture of
polymers in which fluoro-alcohol moieties on an aliphatic cyclic
fluorinated polymer are fully or partially protected with an
alkyloxycarbonylalkyl (AOCA) protecting group, a photoactive
component, and optionally, a base additive. The resin of the novel
photoresist has high transparency in the deep ultraviolet (uv)
region, and such a composition is especially useful for exposure at
193 nanometers (nm) and 157 nm. The invention further relates to a
process for imaging the novel photoresist.
BACKGROUND OF INVENTION
[0002] Photoresist compositions are used in microlithography
processes for making miniaturized electronic components such as in
the fabrication of computer chips and integrated circuits.
Generally, in these processes, a thin coating of film of a
photoresist composition is first applied to a substrate material,
such as silicon wafers used for making integrated circuits. The
coated substrate is then baked to evaporate any solvent in the
photoresist composition and to fix the coating onto the substrate.
The photoresist coated on the substrate is next subjected to an
image-wise exposure to radiation.
[0003] The radiation exposure causes a chemical transformation in
the exposed areas of the coated surface. Visible light, ultraviolet
(UV) light, electron beam and X-ray radiant energy are radiation
types commonly used today in microlithographic processes. After
this image-wise exposure, the coated substrate is treated with a
developer solution to dissolve and remove either the radiation
exposed or the unexposed areas of the photoresist.
[0004] The trend towards the miniaturization of semiconductor
devices has led to the use of new photoresists that are sensitive
at lower and lower wavelengths of radiation and has also led to the
use of sophisticated multilevel systems to overcome difficulties
associated with such miniaturization.
[0005] The present photoresist compositions are positive-working
photoresist, i.e. when they are exposed image-wise to radiation,
those areas of the photoresist composition exposed to the radiation
become more soluble to the developer solution (e.g. a rearrangement
reaction occurs) while those areas not exposed remain relatively
insoluble to the developer solution. Thus, treatment of an exposed
positive-working photoresist with the developer causes removal of
the exposed areas of the coating and the formation of a positive
image in the photoresist coating. Again, a desired portion of the
underlying surface is uncovered.
[0006] Photoresist resolution is defined as the smallest feature
which the resist composition can transfer from the photomask to the
substrate with a high degree of image edge acuity after exposure
and development. In many leading edge manufacturing applications
today, photoresist resolution on the order of less than 100 nm are
necessary. In addition, it is almost always desirable that the
developed photoresist wall profiles be near vertical relative to
the substrate. Such demarcations between developed and undeveloped
areas of the resist coating translate into accurate pattern
transfer of the mask image onto the substrate. This becomes even
more critical as the push toward miniaturization reduces the
critical dimensions on the devices.
[0007] Photoresists sensitive to short wavelengths, between about
100 nm and about 300 nm are often used where subhalfmicron
geometries are required. Particularly preferred are photoresists
comprising non-aromatic polymers, a photoacid generator, optionally
a dissolution inhibitor, and solvent.
[0008] High resolution, chemically amplified, deep ultraviolet
(100-300 nm) positive and negative tone photoresists are available
for patterning images with less than quarter micron geometries. To
date, there are three major deep ultraviolet (uv) exposure
technologies that have provided significant advancement in
miniaturization, and these use lasers that emit radiation at 248
nm, 193 nm and 157 nm. Photoresists for 248 nm have typically been
based on substituted polyhydroxystyrene and its copolymers, such as
those described in U.S. Pat. No. 4,491,628 and U.S. Pat. No.
5,350,660. On the other hand, photoresists for exposure below 200
nm require non-aromatic polymers since aromatics are opaque at this
wavelength. U.S. Pat. No. 5,843,624 and GB 2320718 disclose
photoresists useful for 193 nm exposure. Generally, polymers
containing alicyclic hydrocarbons are used for photoresists for
exposure below 200 nm. Alicyclic hydrocarbons are incorporated into
the polymer for many reasons, primarily since they have relatively
high carbon:hydrogen ratios which improve etch resistance, they
also provide transparency at low wavelengths and they have
relatively high glass transition temperatures. U.S. Pat. No.
5,843,624 discloses polymers for photoresist that are obtained by
free radical polymerization of maleic anhydride and unsaturated
cyclic monomers, but the presence of maleic anhydride makes these
polymers insufficiently transparent at 157 nm.
[0009] Two basic classes of photoresists sensitive at 157 nm, and
based on fluorinated polymers with pendant fluoroalcohol groups,
are known to be substantially transparent at that wavelength. One
class of 157 nm fluoroalcohol photoresists is derived from polymers
containing groups such as fluorinated-norbornenes, and are
homopolymerized or copolymerized with other transparent monomers
such as tetrafluoroethylene (Hoang V. Tran et al Macromolecules 35,
6539, 2002, WO 00/67072, WO 00/17712) using either metal catalyzed
or radical polymerization. Generally, these materials give higher
absorbances but have good plasma etch resistance due to their high
alicylic content. More recently, a class of 157 nm fluoroalcohol
polymers was described in which the polymer backbone is derived
from the cyclopolymerization of an asymmetrical diene such as
1,1,2,3,3-pentafluoro-4-trifluoromethyl-4-hydroxy-1,6-heptadiene
(Shun-ichi Kodama et al Advances in Resist Technology and
Processing XIX, Proceedings of SPIE Vol 4690 p76 2002; WO
02/065212) or copolymerization of a fluorodiene with an olefin (WO
01/98834-A1). These materials give acceptable absorbance at 157 nm,
but due to their lower alicyclic content as compared to the
fluoro-norbornene polymer, have lower plasma etch resistance. These
two classes of polymers can often be blended to provide a balance
between the high etch resistance of the first polymer type and the
high transparency at 157 nm of the second polymer type.
[0010] However, an important limitation to any of these approaches
is the availability of a suitable protecting group for
fluoroalcohols. In almost all of these approaches, the acid labile
protecting groups for the fluoroalcohol moiety has been mainly
limited in scope to either acetal type (e.g. MOM (methoxymethyl),
or tertiaryalkyoxycarbonyl (eg. T-BOC (tert-butyloxycarbonyl) or
tertiary alkyl protecting groups. These protecting groups on the
perfluoroalcohol moiety are relatively unstable and often undergo
partial or complete deprotection during polymerization.
[0011] The difficulty in protecting the fluoroalcohol
functionality, and the resultant loss of the unexposed photoresist
film, has meant that the acid labile functionality can often only
be attached to either a methacrylate, acrylate, or
norbornenecarboxylic acid repeat unit (which are deleterious to
transparency at 157 nm) or to a dissolution inhibitor additive (WO
00/67072, WO 00/17712 Hoang V. Tran et al Macromolecules 35, 6539,
2002). The objective of this invention is to provide a protecting
group which would confer good transparency at 157 nm, and would
possess high thermal stability towards both synthetic and
photoresist processing conditions.
[0012] The inventors of this application have found that,
surprisingly, aliphatic cyclic polymers can have their
fluoroalcohol moieties easily functionalized with an
alkyloxycarbonylalkyl(AOCA) group and that this group provides
these types of resins with surprising advantages for photoresist
applications.
[0013] The AOCA group, particularly the tert-butoxycarbonylmethyl
(BOCME) group, has had some prior use as a substituent in
pharmaceutical applications (WO9533753, DE 2460537). It has also
been employed in resist applications where the BOCME group is
attached to a phenolic moiety in a resin or as small molecule
dissolution inhibitor, and used with radiation at i-line (JP
09211865), 248 nm (JP 20011312065, US6333436B1, US6369276, JP
08193055) or electron beam and X-ray (JP 2000-376059). In addition,
at 248 nm, it also been employed to protect phenolic resins (JP
08176051). Additionally, the BOCME group has been used to protect
some specific monomers for 157 nm photoresists. US 2002/090572 A1
and US2002/0081520 A1 discuss the use of BOCME protected
hexafluorobisphenol-A in silsesquioxane based polymers and
copolymers, which, however, are very absorbent at 157 nm.
Additionally, the use of the BOCME group to protect fluoroalcohol
moieties attached to cyclic or alicyclic polymer repeating units
are disclosed in WO 02/44811 A2 and EP 1,275,666. In WO 01/74916A1,
the abstract discloses a polymer having one segment with an acid
decomposable group, one segment derived from a fluoroacrylate and
another segment derived from other copolymerizable monomer, and the
patent application discloses a large variety of possible polymers.
In WO 02/44811 A2, the BOCME group is used to protect a
norbornenefluoroalcohol group, however, the polymer is used in a
blend with a tetrafluoroethylene copolymer.
[0014] Fluorinated analogs of BOCME
(e.g.--FC(CH.sub.3)CO.sub.2t-Bu) have been described as
substituents for phenol moieties in applications such as herbicides
(EP0044979). US 2002/0061416 discloses the functionalization of the
fluorinated analogue of the BOCME group, but on an acrylate
monomer.
[0015] The present inventors have found that when the AOCA group is
used to protect fluoroalcohol moieties it is unexpectedly found to
possess higher stability towards thermal cleavage than the t-BOC
group or the MOM protecting group. Generally, from a photoresist
standpoint, such an increase in thermal stability of the protected
fluoroalcohol imparted by use of AOCA, particularly the BOCME
group, is desirable as it increases thermal processing latitude and
shelf life. Also, from a synthetic standpoint, such a increase in
thermal stability is desirable as it helps to increase the yield of
protected fluoroalcohol polymers, whether they are made by
protection of pre-formed fluoroalcohol polymers or through
polymerization of monomers containing a fluoroalcohol bearing
polymer protected by AOCA groups. Surprisingly, despite its high
thermal stability, the BOCME protecting group, in particular, can
be easily removed by photoreleased acid in the exposed resist
areas, requiring standard post-exposure bake temperatures to affect
cleavage (1100 C-130.degree. C.). It has also been found by the
applicants that the functionalization of perfluoroalcohols with
AOCA groups results in higher contrast photoresist systems than
using tert-butyl carboxylates of photoresist resins containing
norbornene-5-carboxylic acid repeat units.
SUMMARY OF THE INVENTION
[0016] The present invention relates to a photoresist composition
comprising a photoacid generator and at least one novel polymer
comprising at least one unit as described by structure 1, 2
[0017] where, either
[0018] (i) R1 is an aliphatic cyclic unit of a polymer, R2 is
selected from H, F, (C.sub.1-C.sub.8)alkyl, (C1-C8)fluoroalkyl,
cycloalkyl, cyclofluoroalkyl, and (CR3R4)p(CO)OR5, and R.sub.f is
selected from F, H, (C1-C8)alkyl, or a fully or partially
fluorinated alkyl, and cyclofluoroalkyl, or
[0019] (ii) R1 and R2 combine to form an aliphatic cyclic unit of a
polymer, and R.sub.f is selected from F, H, (C1-C8)alkyl and a
fully or partially fluorinated alkyl, and cyclofluoroalkyl, or
[0020] (ii) R1 and R.sub.f combine to form an aliphatic cyclic unit
of a polymer, and R2 is selected from H, F, (C1-C8)alkyl,
(C1-C8)fluoroalkyl, cycloalkyl, cyclofluoroalkyl, and
(CR3R4)p(CO)OR5; and,
[0021] R3 and R4 are independently H, F, (C1-C8)alkyl,
(C1-C8)fluoroalkyl, cycloalkyl, cyclofluoroalkyl, (CR3R4)p(CO)OR5,
R3 and R4 may combine to form an alkylspirocyclic or a
fluoroalkylspirocyclic group,
[0022] X is selected from (C1-C8)alkylene, (C1-C8)fluoroalkylene,
O(C.sub.1-C8)alkylene, O(C1-C8)fluoroalkylene, cycloalkyl and
fluorinatedcycloalkyl,
[0023] R5 is H or an acid labile group, m=0-1, and p=1-4.
[0024] The invention also relates to a process for imaging the
photoresist composition of the present invention, especially at 157
nm.
DESCRIPTION OF THE INVENTION
[0025] The present invention relates to a novel photoresist
composition comprising a photoacid generator and at least one novel
polymer comprising at least one unit of an aliphatic cyclic
fluoroalcohol group functionalized with an alkyloxycarbonylalkyl
group, as described by structure 1, 3
[0026] where, either
[0027] (i) R1 is an aliphatic cyclic unit of a polymer, R2 is
selected from H, F, (C1-C8)alkyl, (C1-C8)fluoroalkyl, cycloalkyl,
cyclofluoroalkyl, and (CR3R4)p(CO)OR5, and R.sub.f is selected from
F, H, (C1-C8)alkyl, or a fully or partially fluorinated alkyl, and
cyclofluoroalkyl, or
[0028] (ii) R1 and R2 combine to form an aliphatic cyclic unit of a
polymer, and R.sub.f is selected from F, H, (C1-C8)alkyl and a
fully or partially fluorinated alkyl, and cyclofluoroalkyl, or
[0029] (ii) R1 and R.sub.f combine to form an aliphatic cyclic unit
of a polymer, and R2 is selected from H, F, (C1-C8)alkyl,
(C1-C8)fluoroalkyl, cycloalkyl, cyclofluoroalkyl, and
(CR3R4)p(CO)OR5; and,
[0030] R3 and R4 are independently H, F, (C1-C8)alkyl,
(C1-C8)fluoroalkyl, cycloalkyl, cyclofluoroalkyl, (CR3R4)p(CO)OR5,
R3 and R4 may combine to form an alkylspirocyclic or a
fluoroalkylspirocyclic group,
[0031] X is selected from (C1-C8)alkylene, (C1-C8)fluoroalkylene,
O(C.sub.1-C8)alkylene, O(C1-C8)fluoroalkylene, cycloalkyl and
fluorinatedcycloalkyl,
[0032] R5 is H or an acid labile group, m=0-1, and p=1-4.
[0033] This composition is particularly useful for imaging in the
range of 100-300 nm, and more particularly for 157 nm and 193 nm,
and even more particularly for 157 nm. The invention further
relates to a process for imaging the novel photoresist,
particularly at wavelengths in the range 100 nm-200 nm, and more
particularly for imaging at 193 nm and 157 nm.
[0034] In the present application, the functionality
alkyloxycarbonylalkyl (AOCA) is represented by
--(CR3R4)p-CO--O--R5, and the functionality referred to as the
aliphatic cyclic fluoroalcohol is represented by
R1(X)mC(R.sub.fR2)O--H, as shown in structure 1. Typically, the
aliphatic cyclic fluoroalcohol is reacted with a compound capable
of providing the AOCA group to form the novel polymer comprising at
least one unit of structure 1.
[0035] The polymer of the invention may be alkali insoluble or
essentially alkali insoluble, i.e. when R5 is an acid labile group.
Alternatively, the polymer of the invention may be alkali soluble,
i.e. when R5 is hydrogen. When the polymer is alkali soluble a
dissolution inhibitor is required to make the unexposed area
insoluble to the developer. However, when the polymer has an acid
labile group, then during exposure the photoacid generator forms an
acid, which further cleaves the R5 group either by acidolysis or
hydrolysis to give a polymer which is now essentially alkali
soluble. Examples of acid labile groups, without limitation, are
secondary and tertiary alkyls (up to 20 carbon atoms) with at least
one .beta. hydrogen, acetals and ketals, trimethylsilyl, and
.beta.-trimethylsilyl substituted alkyls. Representative examples
of acid labile groups are tert-butyl, tert-pentyl, isobornyl,
1-alkylcyclohexyl, 1-alkylcyclopentyl, cyclohexyl,
2-alkyl-2-admantyl, 2-alkyl-2-norbornyl. Other examples of acid
labile groups are tetrahydrofuranyl, tetrahydropyranyl, substituted
or unsubstituted methoxycarbonyl, .beta.-trialkylsilylalkyl groups
(e.g. CH.sub.2--CH.sub.2Si(CH.sub.3).sub.3,
CH(--CH.sub.2Si(CH.sub.3).sub.3).su- b.2,
CH.sub.2--CH(Si(CH.sub.3).sub.3).sub.2 and the like).
[0036] The polymer of this invention comprises at least one unit of
structure 1, where the unit comprises at least one nonaromatic
aliphatic cyclic group which is part of the polymer backbone and
which may be monocyclic or multicyclic. Aliphatic cyclic groups are
important since they provide the necessary dry etch resistance to
the photoresist. The AOCA group is pendant from an aliphatic cyclic
group which may be multicyclic or monocyclic. In one embodiment of
the invention R1 is a multicyclic or a monocyclic unit which is
part of the polymeric backbone. In another embodiment R1 and R2 or
R1 and R.sub.f combine to form a multi or monocyclic unit, which is
part of the polymeric backbone.
[0037] Typically multicyclic groups are those derived from the
norbornene based monomers, and examples of such multicyclic
monomers that may be used to form the polymer of the present
invention are represented in FIG. 1.
[0038] The multicyclic monomers of FIG. 1 are generic structures of
the multicyclic monomers which are polymerized alone or with other
monomers to give directly the polymer of the invention or
polymerized to give the free fluoroalcohol bearing multicyclic
polymer which can then be capped with the AOCA group.
[0039] Typically such multicyclic monomers are polymerized with an
active metal catalyst, a palladium or nickel complex, such as
described in Hoang V. Tran et al Macromolecules 35 6539, 2002, and
incorporated herein by reference. For the capping of the
fluoroalcohol groups, examples of compounds that can provide the
AOCA group are, without limitation, t-butyl bromoacetate, t-butyl
chloroacetate, t-butyl mesyloxyacetate, t-amyl bromoacetate,
2-methyl-2-adamantyl bromoacetate, 2-methyl-2-norbornyl
bromoacetate, t-butyl 3-bromopropanoate,
t-butyl-2-bromo-2,2-difluorobutanoate.
[0040] The multicyclic unit of FIG. 1 is substituted such that
within the polymer at least one unit has the structure 1, but the
cyclic group may also have other substituents. Typical substituents
are H, F, alkyl, fluoroalkyl, cycloalkyl, fluorocycloalkyl, and
cyano. Additionally, as referred to within FIG. 1, R1 and R2 or R5
and R4 or R6 and R7 substituents may together be part of a
spiroalkyl or fluorospiroalkyl subsituent.
[0041] In the above definition and throughout the present
specification, alkyl means linear or branched alkyl having the
desirable number of carbon atoms and valence. Suitable linear alkyl
groups include methyl, ethyl, propyl, butyl, pentyl, etc.; branched
alkyl groups include isopropyl, iso, sec or tert butyl, branched
pentyl etc. Fluoroalkyl refers to an alkyl group which is fully or
partially substituted with fluorine, examples of which are
trifluoromethyl, pentafluoroethyl, perfluoroisopropyl,
2,2,2-trifluroethyl, and 1,1-difluoropropyl. Alkylene refers to
methylene, ethylene, propylene, etc. Alkylspirocyclic or
fluoroalkylspirocyclic are cyclic alkylene structures connected to
the same carbon atom, preferably where the ring contains from 4 to
8 carbon atoms, and further where the ring may have substituents,
such as F, alkyl, and fluoroalkyl. Cycloalkyl or cyclofluoroalkyl
are defined as aliphatic mono or multi cyclic rings containing
carbon atoms and attached to a carbon atom, preferably cyclobutyl,
cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, norbornyl,
adamantyl, etc., where the ring may be further substituted with
fluorine, alkyl subsituents or fluoroalkyl substituents.
[0042] More specifically, examples of preferred norbornene monomers
containing the t-butoxycarbonylmethyl (BOCME) protecting group with
the t-butyl acid labile group are shown below in FIG. 2, although
other acid labile groups or where R5 from structure 1 is hydrogen,
may also be used.
[0043] In addition to where R1 is the multicyclic unit in the
polymer backbone, monocyclic repeat units may also be used,
although multicyclic units are preferred in some cases. The
monocyclic unit can have a ring structure where the number of atoms
in the ring ranges from about 4 to about 10, preferably from 5 to
about 8, and more preferably from about 5 to about 7.
[0044] In another embodiment, the substituents R1 and R2, or R1 and
R.sub.f in Structure 1 may also combine to give an aliphatic cyclic
polymer, where m=0 or 1, i.e. X may or may not be present as part
of the ring structure. The polymeric cyclic backbone may be
hydrocarbon, or may additionally contain fluorinated substituents.
The monocyclic units may additionally contain oxygen within the
cyclic structure. Generally polymers having monocyclic repeat units
can be made by using radical initiators either in bulk or in a
solvent from suitable monomers, for example, by homopolymerization
of an unconjugated diene or by the copolymerization of a
unconjugated diene with an olefin (For examples of such
polymerization methods see "Cyclopolymerization and Polymers with
Chain Ring Structures, ACS Symposium Series 195 Edited by George
Butler and Jiri E. Kresta, Chapter 2, 3 and 4). Such techniques
could be used to form polymers with monocyclic backbones having the
alcohol functionality either attached to the backbone or as part of
a pendant group as shown in FIG. 3. Possible substituents on the
cyclic structure may be selected from fluorine, alkyl, fluoroalkyl,
cycloalkyl, cyclofluoroalkyl, alicyclic, or fluorinated alicyclic
groups.
[0045] More specifically, the monocyclic polymers of the present
invention could be made by radical homopolymerization of
unconjugated asymmetrical partially fluorinated dienes or by
copolymerization of a fluorinated unconjugated diene with an
olefin, using a radical initiator either in bulk or in a solvent.
(For examples of such polymerization reactions see Shun-ichi Kodama
et al Advances in Resist Technology and Processing XIX, Proceedings
of SPIE Vol 4690 p76 2002; WO 02/065212, or WO 01/98834-A1). In
this manner the desired materials could either be made directly or
through the intermediacy of a fluoroalcohol bearing polymer which
could then be capped with the AOCA group.
[0046] Examples of alcohol or fluoroalcohol sustituents or
substituents containing moieties which are pendant from the cyclic
moiety and which the AOCA group can protect are for example,
without limitation: R1OH, R1 OCH.sub.2(CF.sub.2).sub.nOH (n=1-8),
R1O(CF.sub.2).sub.nOH (n=1-8), R1C(C.sub.nF.sub.2n+1).sub.2OH
(n=1-8), R1OCH.sub.2(C.sub.nF.sub.2n+1).su- b.2OH (n=1-8),
R1CH.sub.2(C.sub.nF.sub.2n+1).sub.2OH (n=1-8).
[0047] Typical examples of aliphatic partially fluorinated
monocyclic monomers having pendant alcohol groups are described in
FIG. 4, where the alcohol groups are further reacted with a
reactant that can provide the AOCA group, preferably a reactant
containing the BOCME functionality, to give the polymer of the
present invention.
[0048] The polymer of the present invention comprises at least one
unit of the structure 1. The polymer is preferably synthesized by
polymerizing a monomer containing the monocyclic or multicyclic
fluoroalcohol functionality, and further reacting the formed
polymer with a compound containing the AOCA group, although it is
within the scope of the present invention that the AOCA capped
monomer may be polymerized to give the polymer of the present
invention.
[0049] It is within the scope of this invention, and preferred,
that the polymer (homopolymer or copolymer with multicyclic or
monocyclic repeat units) is only partially capped with the AOCA
group, thus leaving some of the alcohol groups free and/or some of
the hydroxyl groups capped with a group that is not acid labile,
such as straight chain alkyl groups.
[0050] The polymer may be a homopolymer or may also be a copolymer,
where other monomers are also incorporated into the polymer.
Examples of other monomers having multicyclic repeat units are
norbornene, norbornene derivatives capped with tert-butoxycarboxyl
or alkoxycarbonyl, other nonaromatic aliphatic cyclic monomers and
their derivatives, cyclic fluoralcohols, etc. Additionally for
polymers having multicylic repeat units other units derived from
fluorinated or partially fluorinated olefins may also be present.
Monocyclic polymers comprising at least one unit of the structure 1
may also contain other repeat units derived from substituted
unconjugated dienes and or substituted olefins, which are fully or
partially fluorinated.
[0051] The preferred multicyclic polymers are those derived from
monomers of the type illustrated in structure I or II of FIG. 1, in
which the fluoroalcohol moiety is protected with 2-100% AOCA
groups. The preferred monocyclic polymers are polymers as described
in FIG. 4, and more preferably
poly(1,1,2,3,3-pentafluoro-4-fluoroalkyl-4-hydroxy-1,6-heptadi-
ene) (as in FIG. 4(l)) protected with 2-100% of the AOCA group. The
photoresist composition can comprise a mixture of polymers of the
various embodiments of the present invention.
[0052] It is also within the scope of this invention that the
polymer of the present invention is present in a blend with other
secondary polymers. These secondary polymers may be polymers with
no acid labile groups, polymers with other acid labile groups that
are not AOCA but may have acetal protecting groups such as MOM or
acid cleaveable alkoxycarbonyl (e.g. tert-butoxycarboxyl, t-BOC),
or other polymers or copolymers. Preferably the polymers of this
invention are used without secondary polymers.
[0053] In a preferred embodiment the composition of the present
invention comprises a photoacid generator and a polymer mixture of
an aliphatic monocyclic polymer of this invention with an aliphatic
multicyclic polymer of this invention, preferably, a blend of
poly(1,1,2,3,3-pentaflu-
oro-4-trifluoromethyl-4-hydroxy-1,6-heptadiene) protected with an
AOCA group with
poly(bicyclo[2.2.1]hept-5-en-2-yl)-1,1,1-trifluoro-2-(trifluor-
omethyl)propan-2-ol) protected with the AOCA group, and more
preferably where the capping of the polymer with the AOCA group is
in the range of 2-40%, and even more preferably where the AOCA
group is the BOCME group.
[0054] In another preferred embodiment the polymer mixture
comprises only a multicyclic polymer or only a monocyclic polymer
of the present invention.
[0055] It is within the scope of the present invention that more
than one AOCA group could be present on the same aliphatic cyclic
unit, or that a mixture of AOCA and another acid labile group be
present on the same aliphatic cyclic unit. It is envisaged that two
BOCME or AOCA groups can be present on the same carbon atom (i.e.
C(OC(R').sub.2CO.sub.2-t-Bu).sub- .2).
[0056] Preferred embodiments of the resin composition are as
follows:
poly(bicyclo[2.2.1]hept-5-en-2-yl)-1,1,1-trifluoro-2-(trifluoromethyl)pro-
pan-2-ol) protected with 5-100% BOCME group,
poly(1,1,2,3,3-pentafluoro-4--
trifluoromethyl-4-hydroxy-1,6-heptadiene) protected with 5-100%
BOCME group and a blend of (5-95 weight %) of
poly(bicyclo[2.2.1]hept-5-en-2-yl-
)-1,1,1-trifluoro-2-(trifluoromethyl)propan-2-ol) protected with
5-100% BOCME group mixed with
poly(1,1,2,3,3-pentafluoro-4-trifluoromethyl-4-hyd-
roxy-1,6-heptadiene) protected with 5-100% BOCME group. More
preferably the extent of protection of the polymer by the BOCME
group is in the range from about 9% to about 40%.
[0057] The extent of funtionalization of the polymer with the AOCA
group or the extent of blending with other polymers is determined
by the lithographic properties of the photoresist, in particular
the level of acceptable loss of the unexposed photoresist film
(dark film loss) in the developer, phase compatibility, etc.
Typically the degree of functionalization can range from about 1
mole % to about 100 mole %, and preferably from about 9 mole % to
about 40 mole %.
[0058] The polymers of this invention comprise one or more units
that contain an AOCA protecting group. Upon exposure the AOCA
protecting group undergoes acidolysis or hydrolysis to form a free
carboxylic acid, thereby making the polymer soluble in the alkali
developer for a positive photoresist. The polymer may be capped
with a protecting group after polymerization or the monomer(s) may
be capped with a protecting group and then polymerized. The polymer
may also be inhibited by a dissolution inhibitor, and upon exposure
the photoresist then becomes soluble in the developer. Typically
dissolution inhibitors are added to the photoresist to decrease the
dissolution rate of the unexposed photoresist in the developer. A
polymer of this invention, where R5 is hydrogen, as shown in
structure 1, would be alkali soluble and is useful when mixed with
a dissolution inhibitor and a photoacid generator. Examples of
known dissolution inhibitors that may be used are monomeric or
oligomeric cholates, photoactive compounds which also act as
dissolution inhibitors, such as diarylliodonium or
triphenylsulfonium salts of strong acids in which one or more of
the aryl group has either a hydroxyl subsituent, a carboxylic acid
substituent, or a perfluoroisopropylalcohol substituent protected
with a group susceptible to acidolysis by the release of a
photoacid.
[0059] Transparency of the polymers in a photoresist is an
important requirement. Thus, the absorption coefficient of the
resin film is less than 4/micron at the exposure wavelength,
typically 157 nm, preferably 3/micron and more preferably less than
2/micron and even more preferably less than 1/micron.
[0060] It is preferred if the polymers employed in such
formulations have a weight average molecular weight from about
1,000 to about 200,000, preferably from about 4,000 to about
20,000, more preferably from about 6,000 to about 14,000.
[0061] The photoacid generator (PAG) of the novel composition is
selected from those which absorb at the desired exposure
wavelength, preferably 193 nm and 157 nm. Suitable examples of the
acid generating photosensitive compounds include, without
limitation, ionic photoacid generators (PAG), such as diazonium
salts, iodonium salts, sulfonium salts, or non-ionic PAGs such as
diazosulfonyl compounds, sulfonyloxy imides, and nitrobenzyl
sulfonate esters, although any photosensitive compound that
produces an acid upon irradiation may be used. The onium salts are
usually used in a form soluble in organic solvents, mostly as
iodonium or sulfonium salts, examples of which are diphenyliodonium
trifluoromethane sulfonate, diphenyliodonium nonafluorobutane
sulfonate, triphenylsulfonium trifluromethane sulfonate,
triphenylsulfonium nonafluorobutane sulfonate and the like. Other
compounds that form an acid upon irradiation that may be used, are
triazines, oxazoles, oxadiazoles, thiazoles, substituted 2-pyrones.
Phenolic sulfonic esters, bis-sulfonylmethanes,
bis-sulfonylmethanes or bis-sulfonyldiazomethanes,
triphenylsulfonium tris(trifluoromethylsulfonyl)methide,
triphenylsulfonium bis(trifloromethylsulfonyl)imide,
diphenyliodonium tris(trifluoromethylsulfonyl)methide,
diphenyliodonium bis(trifluoromethylsulfonyl)imide and their
homologues are also possible candidates
[0062] FIG. 4 shows examples of PAG structures, such as onium salts
and hydroxyamic derivatives which are useful.
[0063] The photoresist of the present invention comprises the novel
polymer, a photoacid generator, and optionally a base additive. In
some cases bases or photoactive bases are added to the photoresist
to control the profiles of the imaged photoresist and prevent
surface inhibition effects, such as T-tops. Nitrogen containing
bases are preferred, specific examples of which are amines, such as
triethylamine, triethanolamine, aniline, ethylenediamine, pyridine,
tetraalkylammonium hydroxide or its salts. Examples of
photosensitive bases are diphenyliodonium hydroxide,
dialkyliodonium hydroxide, trialkylsulfonium hydroxide, etc. The
base may be added at levels up to 100 mole % relative to the
photoacid generator. Although, the term base additive is employed,
other mechanisms for removal of acid are possible, for instance by
using tetraalkylammonium salts of volatile acids (eg.
CF.sub.3CO.sub.2.sup.-) or nucleophilic acids (eg Br.sup.-), which
respectively remove acid by volatilization out of the film during
post-exposure bake or by reaction of a nucleophilic moiety with the
acid precursor carbocation (e.g. reaction of tert-butyl carbocation
with bromide to form t-butylbromide).
[0064] FIG. 5 shows the structures of ammonium derivatives which
might be employed as bases.
[0065] The use of non volatile amine additives is also possible.
Preferred amines would be ones having a sterically hindered
structure so as to hinder nucleophilic reactivity while maintaining
basicity, low volatility and solubility in the resist formulation,
such as a proton sponge, 1,5-diazabicyclo[4.3.0]-5-nonene,
1,8-diazabicyclo[5,4,0]-7-undecene, cyclic akylamines, or polyether
bearing amines such as described in U.S. Pat. No. 6,274,286.
[0066] Furthermore, it is within the scope of this invention that
the photoresist further comprises dissolution inhibitors. Thus,
BOCME or AOCA groups could be employed without a protective acid
labile moiety, that is where R5 is hydrogen (e.g.
--CH.sub.2CO.sub.2H). In one embodiment the carboxylic acid could
be present with another unit with the AOCA protecting group and
used to regulate the dissolution rate of the photoresist. In this
concept the amount of AOCA containing units would be determined by
the need to maintain low dark erosion while increasing the
dissolution rate in the exposed areas. Typically, dissolution
inhibitors are added to the photoresist to decrease the dissolution
rate of the unexposed photoresist in the developer.
[0067] The photoresist composition is formed by blending the
ingredients in a suitable photoresist solvent. In the preferred
embodiment, the amount of polymer in the photoresist preferably
ranges from 90% to about 99.5% and more preferably from about 95%
to about 99% based on the weight of the solid; i.e., non-solvent
photoresist components. In the preferred embodiment, the
photoactive compound is present in the photoresist in an amount of
from about 0.5% to about 10% preferably from about 4% to about 6%
based on the weight of the solid photoresist components. In
producing the photoresist composition, the solid components of the
photoresist are mixed with a solvent or mixtures of solvents such
as propylene glycol mono-alkyl ether, propylene glycol alkyl ether
acetate, butyl acetate, xylene, 1,3-di(trifluoromethyl)benzene,
ethylene glycol monoethyl ether acetate, propylene glycol
mono-methyl ether acetate, 2-heptanone, ethyl lactate,
ethyl-3-ethoxypropionate, and mixtures of ethyl lactate and
ethyl-3-ethoxypropionate, among others.
[0068] The prepared photoresist composition solution can be applied
to a substrate by any conventional method used in the photoresist
art, including dipping, spraying, whirling and spin coating. When
spin coating, for example, the photoresist solution can be adjusted
with respect to the percentage of solids content, in order to
provide coating of the desired thickness, given the type of
spinning equipment utilized and the amount of time allowed for the
spinning process. Suitable substrates include silicon, aluminum,
polymeric resins, silicon dioxide, doped silicon dioxide, silicon
nitride, tantalum, copper, polysilicon, ceramics, aluminum/copper
mixtures; gallium arsenide and other such Group 111N compounds. The
photoresist may also be coated over antireflective coatings.
[0069] The photoresist composition solution is then coated onto the
substrate, and the substrate is treated at a temperature from about
70.degree. C. to about 1 50.degree. C. for from about 30 seconds to
about 180 seconds on a hot plate or for from about 15 to about 90
minutes in a convection oven. This temperature treatment is
selected in order to reduce the concentration of residual solvents
in the photoresist, while not causing substantial thermal
degradation of the solid components. In general, one desires to
minimize the concentration of solvents and this first temperature
treatment is conducted until substantially all of the solvents have
evaporated and a thin coating of photoresist composition, on the
order of half a micron (micrometer) in thickness, remains on the
substrate. In a preferred embodiment the temperature is from about
95.degree. C. to about 160.degree. C., and more preferably from
about 95.degree. C. to about 135.degree. C. The treatment is
conducted until the rate of change of solvent removal becomes
relatively insignificant. The temperature and time selection
depends on the photoresist properties desired by the user, as well
as the equipment used and commercially desired coating times. The
coating substrate can then be imagewise exposed to actinic
radiation, e.g., ultraviolet radiation, at a wavelength of from
about 100 nm (nanometers) to about 300 nm, x-ray, electron beam,
ion beam or laser radiation, in any desired pattern, produced by
use of suitable masks, negatives, stencils, templates, etc.
[0070] The photoresist is then subjected to a post exposure second
baking or heat treatment before development. The heating
temperatures may range from about 90.degree. C. to about
160.degree. C., more preferably from about 100.degree. C. to about
130.degree. C. The heating may be conducted for from about 30
seconds to about 5 minutes, more preferably from about 60 seconds
to about 90 seconds on a hot plate or about 15 to about 45 minutes
by convection oven.
[0071] The exposed photoresist-coated substrates are developed to
remove the image-wise exposed areas by immersion in a developing
solution or developed by spray, puddle or spray-puddle development
process. The solution is preferably agitated, for example, by
nitrogen burst agitation. The substrates are allowed to remain in
the developer until all, or substantially all, of the photoresist
coating has dissolved from the exposed areas. Developers include
aqueous solutions of ammonium or alkali metal hydroxides or
supercritical carbon dioxide. One preferred developer is an aqueous
solution of tetramethyl ammonium hydroxide. Surfactants may also be
added to the developer composition. After removal of the coated
wafers from the developing solution, one may conduct an optional
post-development heat treatment or bake to increase the coating's
adhesion and chemical resistance to etching conditions and other
substances. The post-development heat treatment can comprise the
baking of the coating and substrate below the coating's softening
point or UV hardening process. In industrial applications,
particularly in the manufacture of microcircuitry units on
silicon/silicon dioxide-type substrates, the developed substrates
may be treated with a buffered, hydrofluoric acid etching solution
or preferably, dry etching. In some cases metals are deposited over
the imaged photoresist.
[0072] Each of the documents referred to above are incorporated
herein by reference in its entirety, for all purposes. The
following specific examples will provide detailed illustrations of
the methods of producing and utilizing compositions of the present
invention. These examples are not intended, however, to limit or
restrict the scope of the invention in any way and should not be
construed as providing conditions, parameters or values which must
be utilized exclusively in order to practice the present
invention.
EXAMPLES
Glossary
[0073] TGA thermogravimetric analysis
[0074] UV ultraviolet
[0075] MOM methoxymethyl
[0076] MeOH methanol
[0077] mmol millimole ie 10.sup.-3 moles
[0078] BOCME (tert-butoxycarbonyl)methyl
[0079] t-BOC tert-butoxycarbonyl
[0080] THP tetrahydropyranyl
[0081] PAG photoacid generator
[0082] IPA isopropyl alcohol
[0083] THF tetrahydrofuran
[0084] TMAH tetramethylammonium hydroxide
[0085] t-BuOK potassium tert-butoxide
[0086] BHTTP
3-(bicyclo[2.2.1]hept-5-en-2-yl)-1,1,1-trifluoro-2-(trifluoro-
methyl)propan-2-ol,
[0087] CMAdOM Carb-2-methyl-2adamantyloxymethyl,
[0088] PBTTP
Poly(3-(bicyclo[2.2.1]hept-5-en-2-yl)-1,1,1-trifluoro-2-(trif-
luoromethyl)propan-2-ol), purchased from Promerus LLC 9921
Brecksville Road, Bldg B, Brecksville Ohio 44141 4
[0089] PTHH
1,1,2,3,3-pentafluoro-4-trifluoromethyl-4-hydroxy-1,6-heptadie- ne
PPTH H
poly(1,1,2,3,3-pentafluoro-4-trifluoromethyl-4-hydroxy-1,6-hepta-
diene) which is a mixture of 5 and 6 membered rings, purchased from
Asahi Glass Co, LTD, 2-1-2 Marunouchi, Chiyoda-ku Tokyo 100-8305
Japan, 5
Example 1
[0090] Table 1 shows the TGA onset of deprotection of MOM and t-boc
compared to that found for the deprotection with the BOCME group on
representative examples of polymers (FIG. 6) belonging to the two
classes of cyclic fluoroalcohol bearing polymer described
earlier.
1TABLE 1 Onset of deprotection of polymers I and II with various
protecting groups* Protecting Polymer Onset of group (% protection)
Deprotection (.degree. C.) BOCME II (30%) 174 BOCME I (30%) 206
T-BOC I (30%) 120 MOM II (20%) <100 *Data gathered at 20.degree.
C./min heating rate
[0091] Table 1 clearly shows that polymers with the BOCME group
thermally deprotect at a higher temperature than the same polymer
with the t-boc and MOM groups
Example 2
[0092] The contrasts of resists were measured by coating them at a
thickness of 1350 A (Angstroms) and after exposure using an open
frame reticle baking and developing the film and measuring the
normalized thickness as a function of dose. The contrast is taken
from the slope of plot of normalized thickness versus log(dose).
Processing conditions were as follows:
[0093] The exposures were done an Exitech 157 nm small field
(1.5.sub.--1.5 mm2) mini-stepper (0.6 NA) using open frame exposure
reticle at International SEMATECH in Austin. An FSI Polaris 2000
track was used to coat, bake, and develop the resist films. A
Prometrix interferometer was used to measure resist thickness.
[0094] The photoresist formulations preparation and resultant
contrasts are as follows:
[0095] By mixing the following dry ingredients poly(tert-Butyl
Bicyclo[2.2.1]hept-5-ene-2-carboxylate-co-1,1,1-trifluoro-2-(trifluoromet-
hyl)pent-4-en-2-3-(Bicyclo[2.2.1]hept-5-en-2-yl)-1,1,1-trifluoro-2-(triflu-
oromethyl)propan-2-ol) (75.3%) poly(tert-Butyl
3-(trifluoromethyl)tricyclo-
[4.2.1.02,5]non-7-ene-3-carboxylate-co-carbon monoxide (18.8%),
triphenylsulfonium nonaflate (5.6%) and tetramethyammonium acetate
(0.3%) as a 10% solution in propyleneglycol methylether acetate
gives contrasts of 6-7 while similar formulations containing as dry
ingredients 93%
poly(1,1,1-trifluoro-2-(trifluoromethyl)pent-4-en-2-3-(Bicyclo[2.2.1]hept-
-5-en-2-yl) functionalized with BOCME (20% protection) (93%
solids), triphenylsulfonium nonaflate (5.6%) and
tetramethylammonium acetate (0.5%) typically give contrasts of
.about.12-25 using different PAB's (from 135-150.degree. C.) or PEB
(115-150) and developments times of 30 seconds with 0.26 N
tetramethylammonium hydroxide.
Example 3
Synthesis of BOCME Protected
Poly(3-(bicyclo[2.2.1]hept-5-en-2-yl)-1,1,1-t-
rifluoro-2-(trifluoromethyl)propan-2-ol) Using t-BuOK
[0096]
Poly(3-(bicyclo[2.2.1]hept-5-en-2-yl)-1,1,1-trifluoro-2-(trifluorom-
ethyl)propan-2-ol) (PBHTTP) (4.0 g, 14.59 mmol) was dissolved into
15 ml of tetrahydrofuran (THF), and solid t-BuOK (0.491 g, 4.38
mmol) was added while stirring. After 30 minutes, t-butyl
bromoacetate (1.71 g, 8.76 mmol) was added to this reaction
solution which was stirred for 16 hours at 25.degree. C. After
removal of the solvent using a rotary evaporator, the resultant
residue was dissolved in 20 ml of methanol (MeOH) containing 1.0 g
of concentrated HCl. This solution was then precipitated in 180 ml
of water-methanol (8:1). The polymer was isolated by filtration and
further purified by dissolving it into MeOH and re-precipitating it
in the water-methanol mixture. The final precipitate was then
filtered, washed with water and dried overnight under vacuum (25"
Hg) at 55.degree. C. The isolated yield of polymer was 91%. The
presence of t-butyl and methylene groups were confirmed by
.sup.1H-NMR (ppm, acetone-d.sub.6) .delta. 1.48 (9H, t-butyl) and
.delta.4.27 (2H, --CH.sub.2--COO--). The extent of protection with
BOCME group was found to be 24 mole %.
Example 4
Synthesis of BOCME protected
Poly(3-(bicyclo[2.2.1]hept-5-en-2-yl)-1,1,1-t-
rifluoro-2-(trifluoromethyl)propan-2-ol) using TMAH.5H.sub.2O
[0097] PBHTTP (4.0 g, 14.59 mmol) was dissolved in 15 ml of THF and
solid TMAH.5H.sub.2O (0.793 g, 4.38 mmol) was added while stirring.
After 30 minutes, t-butyl bromoacetate (1.71 g, 8.76 mmol) was
added to this solution which was stirred for another 16 hours at
25.degree. C. The precipitate formed in the reaction mixture was
removed by filtration. The resultant filtrate was stripped of
solvents in a rotary evaporator. The resultant residue was
redissolved in 20 ml of MeOH containing 1.0 g of concentrated HCl.
This solution was precipitated in 180 ml of water-methanol (8:1)
mixture. The polymer was isolated by filtration and further
purified by dissolving it into MeOH and re-precipitating it in the
water-methanol mixture. The final precipitate was then filtered,
washed with water and dried overnight under vacuum (25" Hg) at
55.degree. C. The isolated yield of polymer was 91%. The presence
of t-butyl (1.48 ppm) and methylene (4.27 ppm) groups were
confirmed by .sup.1H NMR. The extent of protection with BOCME group
was found to be 28 mole
Example 5
Synthesis of BOCME protected PBHTTP using 25% aqueous TMAH
[0098] PBHTTP (4.0 g, 14.59 mmol) was dissolved in 15 ml of THF and
25% aqueous tetramethylammonium hydroxide (TMAH) (1.6 g, 4.38 mmol)
was added while stirring. After 30 minutes, t-butyl bromoacetate
(1.71 g, 8.76 mmol) was added to this reaction solution which was
stirred for 16 hours at 25.degree. C. After removal of the solvent
using a rotary evaporator, the resultant residue was dissolved in
20 ml of MeOH containing 1.0 g of concentrated HCl. This solution
was then precipitated in 180 ml of water-methanol (8:1) mixture.
The polymer was isolated by filtration and further purified by
dissolving it into MeOH and re-precipitating it in the
water-methanol mixture. The final precipitate was then filtered,
washed with water and dried overnight under vacuum (25" Hg) at
55.degree. C. The isolated yield of polymer was 92%. The presence
of t-butyl (1.48 ppm) and methylene (4.27 ppm) groups were
confirmed by .sup.1H NMR. The extent of protection with BOCME group
was found to be 21 mole %.
Example 6
Synthesis of BOCME Protected PBHTTP using 25% TMAH in MeOH
[0099] PBHTTP (4.0 g, 14.59 mmol) was dissolved in 15 ml of THF and
the 25% TMAH in methanol (1.6 g, 4.38 mmol) was added while
stirring. After 30 minutes, t-butyl bromoacetate (1.71 g, 8.76
mmol) was added to this reaction solution which was stirred for 16
hours at 25.degree. C. After removal of the solvent using a rotary
evaporator, the resultant residue was dissolved in 20 ml of MeOH
containing 1.0 g of concentrated HCl. This solution was then
precipitated in 180 ml of water-methanol (8:1). The polymer was
isolated by filtration and further purified by dissolving it into
MeOH and re precipitating it in the water-methanol mixture. The
final precipitate was then filtered, washed with water and dried
overnight under vacuum (25" Hg) at 55.degree. C. The isolated yield
of polymer was 90%. The presence of t-butyl (1.48 ppm) and
methylene (4.27 ppm) groups were confirmed by .sup.1H NMR. The
extent of protection with BOCME group was found to be 22 mole
%.
Example 7
Synthesis of BOCME protected PBHTTP using K.sub.2CO.sub.3 and
18-crown-6 Ether
[0100] A solution was prepared in a small round bottomed flask
consisting of the PBHTTP (2.0 g, 7.29 mmol), t-butyl bromoacetate
(1.42 g, 7.29 mmol), and 18-crown-6 ether (0.19 g, 0.73 mmol)
dissolved in 6 ml of dry THF under nitrogen equipped with a reflux
column, a magnetic stirring bar and a heating mantle. To this
solution was added anhydrous K.sub.2CO.sub.3 (1.26 g) and the
solution was vigorously stirred overnight, while under reflux.
After this time the reaction mixture was filtered and the filtrate
was stripped of solvents in a rotary evaporator. The filtrate was
then re-dissolved into 40 ml of ethyl acetate and washed with
several 10 ml aliquots of distilled water until a neutral pH was
detected in the water washings. The washed ethyl acetate solution
was stripped of solvents in a rotary evaporator and further dried
under 1 torr of vacuum at 35.degree. C. for an hour producing a
hard foam. This foam was re-dissolved in 30 ml of THF and
precipitated into 300 ml of distilled water. This material was
filtered, washed with distilled water and air dried for an hour.
The recovered material was re-precipitated in the same fashion two
more times. The final precipitate was then dried under vacuum (25"
Hg) at 55.degree. C., overnight. The isolated yield of the polymer
was 62%. The presence of t-butyl (1.48 ppm) and methylene (4.27
ppm) groups were confirmed by .sup.1H NMR. The extent of protection
of the polymer with BOCME group was found to be 100 mole
Example 8
Synthesis of
poly(1,1,2,3,3-pentafluoro-4-trifluoromethyl-4-hydroxy-1,6-he-
ptadiene) from its Methoxymethyl Derivative
[0101] Ten grams of
poly(1,1,2,3,3-pentafluoro-4-trifluoromethyl-4-hydroxy-
-1,6-heptadiene) protected with 20% of MOM group was dissolved in
30 ml of THF and mixed with 10 ml of trifluoroacetic acid and 7.5
ml of water. This homogeneous solution was stirred overnight at
room temperature. After reaction the solvents were stripped at
50.degree. C. in a rotary evaporator. The residue was dissolved in
30 ml of IPA and precipitated in 750 ml of cold water. The
precipitate was filtered, washed and dried under vacuum (25" Hg) at
55.degree. C. The isolated yield of the polymer was 98%. NMR
analysis confirmed the absence of MOM group.
Example 9
Synthesis of BOCM E protected
poly(1,1,2,3,3-pentafluoro-4-trifluoromethyl-
-4-hydroxy-1,6-heptadiene) using t-BuOK
[0102]
Poly(1,1,2,3,3-pentafluoro-4-trifluoromethyl-4-hydroxy-1,6-heptadie-
ne) (4.0 g, 14.81 mmol) (PPTHH) from Example 8 was dissolved in 15
ml of THF and to this solution was added solid t-BuOK (0.5 g, 4.44
mmol) while stirring. After 30 minutes, of stirring at 25.degree.
C., t-butyl bromoacetate (1.74 g, 8.88 mmol) was added to this
reaction solution and it was stirred for another 16 hours at
25.degree. C. After this time, the precipitate formed during the
reaction was removed by filtration. The resultant filtrate was then
stripped of solvent in a rotary evaporator. The residue was
re-dissolved in 20 ml of MeOH containing 1.0 g of concentrated HCl.
This solution was then precipitated in 200 ml of 15% MeOH in water.
The precipitate was filtered, washed with distilled water and
dried. The polymer was further purified by re-dissolving it in MeOH
and re-precipitating it in water. After drying under vacuum (25"
Hg) at 55.degree. C., the yield of polymer was 92%. The presence of
t-butyl (1.48 ppm) and methylene (4.27 ppm) groups were confirmed
by .sup.1H NMR. The extent of protection with BOCME group was found
to be 22 mole %.
Example 10
Synthesis of BOCME Protected PPTHH Using TMAH.5H.sub.2O
[0103] PPTHH (4.0 g, 14.81 mmol) from Example 8 was dissolved in 15
ml of THF and to this solution was added solid TMAH.5H.sub.2O (0.81
g, 4.44 mmol) while stirring. After 30 minutes, of stirring at
25.degree. C., t-butyl bromoacetate (1.74 g, 8.88 mmol) was added
to this reaction solution and stirred for another 16 hours at
25.degree. C. After this time, the precipitate formed during the
reaction was removed by filtration. The resultant filtrate was then
stripped of solvent in a rotary evaporator. The residue was
re-dissolved in 20 ml of MeOH containing 1.0 g of concentrated HCl.
This solution was then precipitated in 200 ml of 15% MeOH in water.
The precipitate was filtered, washed with distilled water and
dried. The polymer was further purified by re-dissolving it in MeOH
and re-precipitating it in water. After drying under vacuum (25"
Hg) at 55.degree. C., the yield of polymer was 92%. The presence of
t-butyl (1.48 ppm) and methylene (4.27 ppm) groups were confirmed
by .sup.1H NMR. The extent of protection with BOCME group was found
to be 23 mole
Example 11
Synthesis of CMAdOM Protected
poly(1,1,2,3,3-pentafluoro-4-trifluoromethyl-
-4-hydroxy-1,6-heptadiene) Using 2-Methyl-2-adamantyl
Bromoacetate
[0104] The polymer (2.0 g, 7.4 mmol) from Example 8 was dissolved
in 12 ml of THF and TMAH.5H.sub.2O (0.4 g, 2.22 mmol) was added
while stirring. After 30 minutes, 2-methyl-2-adamantyl bromoacetate
(1.28 g, 4.44 mmol) was added to this reaction solution and stirred
for 16 hours at 25.degree. C. The solid formed in the reaction
mixture was separated by filtration. The solvent in the filtrate
was then stripped of solvent in a rotary evaporator and the residue
was dissolved in 20 ml of MeOH containing 1.0 g of concentrated
HCl. It was precipitated in 200 ml of 15% MeOH in water. The
precipitate was filtered, washed with water and dried. The polymer
was further purified by dissolving in MeOH and re-precipitating in
water. The polymer was dried under vacuum (25" Hg) at 55.degree. C.
The yield of polymer was 90%. The presence of 2-methyl-2-adamantyl
(1.5-2.0 ppm) and methylene (4.27 ppm) groups were confirmed by
.sup.1H NMR. The extent of protection was found to be 25 mole
%.
Preparation of Photoresist Solution and Imaging at 157 nm
[0105] The imaging work was done with an Exitech 157 nm small field
(1.5 .sub.--1.5 mm2) mini-stepper (0.6 NA) using a phase-shift mask
(.sigma.0.3) at International SEMATECH in Austin, Tex. A JEOL
JWS-7550 was used to obtain scanning electron micrographs. A
Hitachi 4500 Microscope was used to obtain cross-sectional data. An
FSI Polaris 2000 track was used to coat, bake, and develop the
resist films. A Prometrix interferometer was used to measure resist
thickness.
Example 12
Resist solution containing PBTTP
[0106] A solution was prepared from 6.58 wt % PBTTP as prepared in
example 4, 0.39 wt % triphenylsulfonium triflate, 0.03 wt %
tetramethyammonium acetate and 93 wt % propyleneglycolmonomethyl
ether acetate (PGMEA). This solution was filtered through a 0.2
micron PTFE filter.
Example 13
Resist solution containing PPTHH
[0107] A solution was prepared from 6.58 wt % PPTHH as prepared in
example 10, 0.39 wt % triphenylsulfonium triflate, 0.03 wt %
tetramethyammonium acetate and 93 wt % PGMEA. This solution was
filtered through a 0.2 micron PTFE filter.
Example 14
Resist Solution Containing a 50/50 Mixture of PBTTP and PPTHH
[0108] A solution was prepared from 3.29 wt % PBTTP, as prepared in
example 4, 3.29 wt % PPTHH, as prepared in example 10, 0.39 wt %
triphenylsulfonium triflate, 0.03 wt % tetramethyammonium acetate
and 93 wt % PGMEA. This solution was filtered through a 0.2 micron
PTFE filter.
Example 15
Imaging of Photoresist Solution Containing PBTTP
[0109] The photoresist solution prepared in example 12 was spin
coated at 1658 rpm onto separately a bare silicon and a wafer
coated with an organic antireflective coating. After post applied
bake, 130.degree. C./60s, a thickness of 1350 A resulted. After
exposing at 157 nm using an open frame reticle, a post exposure
bake of 115C/90s, and a development for 30s in 0.26 N TMAH were
applied. This resulted in an exposure response curve from which a
clearing dose of 7.2 mJ/cm.sup.2 and a contrast of 12 was obtained.
The wafer coated onto the antireflective coating coated silicon was
exposed using a phase shift mask and the same processing conditions
to give a resolution of 100 nm for 1:1.5 lines and spaces having a
line width of 108 nm and an exposure dose of 51 mJ/cm.sup.2.
Example 16
Imaging of resist solution containing PPTHH
[0110] The resist solution prepared in example 13 was spin coated
at 2220 rpm separately onto a bare silicon and a wafer coated with
an organic antireflective coating. After a post applied bake of
150.degree. C./60s a thickness of 1350 A resulted. After exposing
at 157 nm using an open frame reticle, a post exposure bake of
135C/90s, and a development for 30s in 0.26 N TMAH, were applied.
This resulted in an exposure response curve from which a clearing
dose of 8.1 mJ/cm.sup.2 and a contrast of 12 was obtained. The
wafer coated onto the antireflective coating coated silicon was
exposed using a phase shift mask and the same processing conditions
to give resolution of 100 nm for 1:1.5 lines and spaces having a
line width of 73 nm and an exposure dose of 69 mJ/cm.sup.2.
Example 17
[0111] Imaging of Resist Solution Containing a 50/50 mixture of
PBTTP and PPTHH
[0112] The resist solution prepared in example 14 was spin coated
at 1801 rpm separately onto a bare silicon and a wafer coated with
an organic antireflective coating. After a post applied bake of
150C/60s, a thickness of 1350 A resulted. After exposing at 157 nm
using an open frame reticle, a post exposure bake of 135C/90s, and
a development of 30s in 0.26 N TMAH, were applied. This resulted in
an exposure response curve from which an exposure dose of 10.2
mJ/cm.sup.2 and a contrast of 10.2 were obtained. The wafer coated
onto the antireflective coating coated silicon was exposed using a
phase shift mask and the same processing conditions to give
resolution of 100 nm for 1:1.5 lines and spaces having a line width
of 80 nm and an exposure dose of 81 mJ/cm.sup.2.
* * * * *